Knotweed

Weather chills Derry's war against Japanese knotweed

DERRY—Mother Nature has caused a delay in a plan by the Conservation Commission to chart the progress of Japanese knotweed, a non-native weed that is growing all over town.

Increasingly cold temperatures and the arrival of frost have made it more difficult to identify knotweed(Polygonum sachalininese), said commission member James Arruda.

"It's a very distinctive plant while it's actively growing," Arruda said. "I know what it looks like, but the average individual doesn't."

The commission had launched a "knotweed attack" plan to identify where it's growing in Derry and develop a map. Commission members helped coordinate the effort as residents were asked to identify the weed if it was growing on their property.

Plans called for completing some of the work by the end of this month. Residents can still try to identify where it is growing, but it would probably be better to wait until the spring, said Commission Chair Margaret Ives.

Knotweed has sprouted up all over town and will require a lengthy campaign to eventually eradicate it.

"This is really an epidemic, " Ives said. It's going to take a couple of years. This is not a quick fix."

Introduced from Asia, Japanese Knotweed, or Japanese Bamboo as it also known, first appeared in the area in the early 1800s, Ives said. Japanese Knotweed can choke off other native plants, cause soil erosion and even sprout up through concrete and asphalt, according to horticultural experts.

During the fall, the plant has small greenish white flowers and can be found, among other places, near Island Pond Road and all along the Route 102 corridor, Arruda said.

The best time to control the plant is from July 1 to the first killing frost.

Ives said residents who find the noxious weed and still want to remove it should, "cut it, bag it and take it to the dump."

At the transfer station, it should be disposed of with the garbage and not with leaves, she added.

After it's cut, Japanese knotweed shouldn't be allowed to remain on the lawn. Ives said merely cutting the plant isn't enough as it can still spread, unlike some other species.

"It is important when you cut it to take it off your property," Ives said. "Don't dump it anywhere; make sure it goes to the transfer station because they are set to take it."

To prevent the spread and help with eradication, residents are being asked to use Roundup, Ives said, though the product shouldn't be used near water.

As part of the campaign to eradicate knotweed, Arruda has worked with IT Director Doug Rathburn to develop a map that is divided into grids. Residents have been asked to take a grid or parcel and locate on the map were the knotweed lies.

Residents can still turn in grids to Arruda, who said he has about a dozen people to contact. He said he hopes to work with Rathburn to develop a map. "That will go on through the winter," Arruda said.

Because the knotweed presence is so extensive throughout town, Arruda said it would be helpful if more volunteers participated. He suggested residents wait, though, through the fall and winter and then be ready to address the problem in the spring.

Arruda and Ives said the knotweed problem isn't limited to Derry, but is spread throughout the state and New England.Residents wanting more information on Japanese knotweed can contact Doug Cygan, an invasive species coordinator/entomologist II for the New Hampshire Department of Agriculture. Cygan can be reached at doug.cygan@agr.nh.